I'm stressed about my eco. exam tom. , what to do to let go off of that stress and tension which is not even letting me study with full confidence ?

First of all do not panic at all. Economics as a subject if understood carefully can be quite interesting to study and grasp. We, at Meritnation, have developed the study material of Economics- XI especially knowing typicality of this subject. We know most of the students find it quite difficult. In this regard, the study material that has been developed is very self-explanatory. In addition to this, we also have numerous interactive videos and lots of practice questions. To begin with go through the various lessons and chapters. Try making notes of the important points. This will help you to grasp the topics in a better manner. After finishing every chapter take up the chapter tests. This will help you to test yourself and identify the topics that require more attention. As you move on to the subsequent chapters do not forget to frequently revise the previous ones with the help of revision notes. This will help you to retain the various concepts. This will boost your confidence and will improve your performance. In the process, if you get stuck somewhere, then you can get your doubts cleared by our experts. 
All the best!!